Answer:
The partial sum is 561
Step-by-step explanation:
Given:
The arithmetic series = 9+12+15...+51+54+57
Partial sum between 9 and 57, with d=3
To Find :
The partial sum = ?
Solution
The given series is a arithmetic series with difference 3.
So the series is
9,12,15,18,21,24,27,30,33,36,29,42,45,48,52,51,54,57
Thus There are 17 terms,
Here the is a middle term is the the ninth,
The 9 term is
[tex]a_ 9 = a_0 +(n-1)d[/tex]
[tex]a_ 9 = 9 +(9-1)3[/tex]
[tex]a_ 9 = 9 +(8)3[/tex]
[tex]a _9 = 33[/tex]
Now the
The partial sum is 33 x 17 = 561
